[8.04] The Distance and Stellar Populations of And VI, A New Local Group Dwarf Spheroidal Galaxy Near M31

G. H. Jacoby, T.E. Armandroff (KPNO/NOAO), J.E. Davies (JHU)

We will present our 4-m discovery images of And VI, a new
Local Group dwarf galaxy near M31 identified using a digital
filter technique applied to the digitized POSS-II sky
survey. Based on deep follow-up B-, V-, and I- band
imaging at the 3.5-m WIYN telescope, we will report our
estimates for the distance, mean metallicity and age, and
spread in metallicity and age for the stars in And VI.

The non-detection of sources in our 4-m H\alpha images,
combined with IRAS flux limits, argues against the presence
of significant star forming regions that would indicate this
galaxy is a dwarf irregular. Rather, the resemblance of And
VI to other dwarf spheroidals in the vicinity of M31 (And I,
II, III, and V) argues that And VI also is a dwarf
spheroidal.

And VI was independently reported by Karachentsev &
Karachentseva (1998) but designated as Pegasus Dw; an
initial V-I CMD has been presented by Grebel &
Guhathakurta (ApJL, submitted) that indicates a physical
association with M31. Here, we refine the results of that
study, both in regard to distance and metallicity.

At a projected distance of 271 kpc from M31, And VI is
nearly twice as far from M31 as the next most distant dwarf
spheroidal previously known (And II). This extreme distance,
combined with And VI's close proximity to a bright star,
probably explains its delayed discovery. Our (not yet
completed) survey extends somewhat beyond the projected
distance of And VI, and when completed may reveal additional
dwarfs. However, it may be necessary to extend surveys for
M31 dwarfs to even greater projected radii to ensure
completeness. Our technique, using the digitized POSS-II,
provides a quick and effective approach to finding very low
surface brightness dwarf galaxies.

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